If identical twins had babies with identical twins, would the children be biologically siblings?
Biologically they'd be full siblings, if their twin parents married singlets their cousins would be biologically half siblings.
If a girl slept with two identical twins and got pregnant, would both twins...?
I Think the Careful Analysis of the DNA (Germline), Would Reveal Some Difference. E. g., the Incorporation, of Viral DNA.
Are identical twins more common than fraternal twins?
No, about 1 in every 3 twins is an identical twin.Source: http://twins.usc.edu/about.htm
Which is more common fraternal twins or identical twins?
Fraternal twins are more popular.